Metzman510 Posted February 21, 2020 Report Share Posted February 21, 2020 New to the forum, but have been using it as a resource for a while, it is a real help! My 69 510 sedan has a 5-speed in it. Due to packaging restraints in the car, I am having trouble identifying it. The serial number on the top of the bell housing is 7202575, there is not a number cast into either side of the transmission housing (60 or 60A as an example). The tail housing is marked #1, and the trans case has "L1 NMCA" cast in the side of it. The speedometer drive is in the tail housing, on a downward angle, pointing to the left side, and the screw to hold the speedo pinion drive in is at 6 o'clock. L-series engine in the car. Trans is definitely a wide ratio unit, standard 5-speed H and a half pattern (not the dogleg). Quote Link to comment
datzenmike Posted February 21, 2020 Report Share Posted February 21, 2020 NMCA.... Nissan Motorcar Company Australia casting '80 or newer. Most likely an FS5W71B with front and rear case sandwiching a 1" thick steel adapter plate. If by 'left side' speedometer you mean left when sitting in the car then it's a 26" long 720 'shorty' with an L series front case put on it. Quote Link to comment
Metzman510 Posted February 21, 2020 Author Report Share Posted February 21, 2020 Okay, I'll get under there tonight and put a tape measure to it, thanks Mike! Yes, on the left as you are sitting in the car. I found a thread discussing speedometer pinion drives here: If you go to the top of page 4, in the picture are the 2 speedometer drive assemblies. Mine looks like the one on the left. Mine has a white 19 tooth gear on the end of it. I am trying to ID the trans, as my speedometer is way off (100 mph indicated is actual 65 mph GPS). So I was hoping to get a correction on the speedometer pinion. My diff is an open R-180 front unit from a 4x4 pickup with 4:11 gearing, tire size is 195/60-r14. All guidance is appreciated! Quote Link to comment
datzenmike Posted February 22, 2020 Report Share Posted February 22, 2020 100/65 is likely the speedometer unit in the dash. Has this speedometer ever worked properly? I'm guessing this is the way it came to you??? Quote Link to comment
datzenmike Posted February 22, 2020 Report Share Posted February 22, 2020 This is probably the 5 speed you have. Note the speedo on left side. 2 Quote Link to comment
Metzman510 Posted February 22, 2020 Author Report Share Posted February 22, 2020 Yes, when I bought the car the speedo cable was in the trunk, when I connected it, this is how it reads. Going out to check th trans pic against what's in the car. Quote Link to comment
Metzman510 Posted February 23, 2020 Author Report Share Posted February 23, 2020 That is the transmission in my 510. So can I assume that is the FS5W71B "shorty" from a 1984(ish) 720 pickup? Quote Link to comment
datzenmike Posted February 23, 2020 Report Share Posted February 23, 2020 What the shortys came in is only a guess but I would say the '83 and up 720. But I don't believe it was ever offered on the '80 model year with an L20B engine, thus the front case has been swapped onto it and your is from a 2wd as it has the speedometer drive in it. The 4x4 speedometer is driven from the transfer case. I have a short 4x4 and it was in a 720 KC 1 Quote Link to comment
Metzman510 Posted February 23, 2020 Author Report Share Posted February 23, 2020 So you think I should work on the speedometer gauge to try and correct the indicator vs actual speed issue? I need to check, but I think the odo is running fast also which makes me think the speedo drive gear is causing the problem. Does anyone still make those geared correction units that you run inline on the speedo drive cable? Quote Link to comment
Metzman510 Posted February 23, 2020 Author Report Share Posted February 23, 2020 Does anyone know what the thread sizes are on either end of a Datsun speedometer cable? Quote Link to comment
datzenmike Posted February 23, 2020 Report Share Posted February 23, 2020 100 when going 65 is 53% too fast. You have a 19 tooth pinion drive gear. To slow it down 53 % you would need a 29 tooth pinion.... there are no such things. I have an orange 22 tooth and that was a bitch to find. Likely the spinning magnet inside the copper cup inside the speedometer gauge is rubbing and rather that magnetism turning the cup Quote Link to comment
Metzman510 Posted February 23, 2020 Author Report Share Posted February 23, 2020 Any information or documentation floating around on adjusting the magnets in the speedometer? The needle on the gauge reads steady BTW. Quote Link to comment
Crashtd420 Posted February 23, 2020 Report Share Posted February 23, 2020 8 hours ago, Metzman510 said: So you think I should work on the speedometer gauge to try and correct the indicator vs actual speed issue? I need to check, but I think the odo is running fast also which makes me think the speedo drive gear is causing the problem. Does anyone still make those geared correction units that you run inline on the speedo drive cable? They do make them, I am using one on my stumpy 5spd in my 521.. fyi the speedo drive is not like the other 71b transmissions... the are longer... I'll have to dig out the info.... the company I bought it from no longer has a supporting website, so I'm not sure what's up with that.... 1 Quote Link to comment
Crashtd420 Posted February 23, 2020 Report Share Posted February 23, 2020 (edited) This is them.... Just call them.... super nice people... pretty sure it's just a husband and wife team... The threads are M22 x1.5 (the .5 thread pitch is a typo) To check your accuracy the ask for a ten mile check..... I used the mile markers on the highway..... so check your mileage and you tell them the variance so if you went 11 on the odometer on a 10 mile road that's what you tell them and they build the appropriate ratio.... Be aware the ten mile test will correct the odometer but the speedometer might still be a little off if it also needs recalibrating.... Edited February 23, 2020 by Crashtd420 1 Quote Link to comment
Crashtd420 Posted February 23, 2020 Report Share Posted February 23, 2020 Look them up as Apt Instruments... They are there but website is gone... 1 Quote Link to comment
Crashtd420 Posted February 23, 2020 Report Share Posted February 23, 2020 These guys claim to have m22 metric ones coming soon.... http://www.texasindustrialelectric.com/400_18_90_Degree_Metric_Speedometer_Adapter.asp 1 Quote Link to comment
Metzman510 Posted February 23, 2020 Author Report Share Posted February 23, 2020 Crashtd420, Excellent info, thank you so much! Will call on Monday and now have a great reason to go for a drive! Quote Link to comment
datzenmike Posted February 23, 2020 Report Share Posted February 23, 2020 The odometer is driven mechanically from the speedometer cable so it will read what the transmission sends it. The needle has a light spring then pulls it to zero. It's mounted on a cup made of copper. Inside the cup is a magnet turned directly by the speedometer cable. The cable spins the magnet which induces currents in the copper. These induced currents produce a magnetic field which interacts with the spinning magnets and the cup is 'pulled' in the direction of the spinning magnets. Think of an automatic torque converter where the ATF is the magnetic field. The engine turns the turbine and the ATF turns the stator even though they are not directly coupled. In a speedometer the magnets are spinning much faster than the speedometer needle so if there was dirt inside and the magnets were rubbing the cup (for example) the cup would spin much faster than it should. Possibly the return spring is broken? Definitely drive a known distance. The odometer should read close to correct proving the actual mileage versus the needle reading. 1 Quote Link to comment
MikeRL411 Posted February 23, 2020 Report Share Posted February 23, 2020 12 hours ago, Metzman510 said: So you think I should work on the speedometer gauge to try and correct the indicator vs actual speed issue? I need to check, but I think the odo is running fast also which makes me think the speedo drive gear is causing the problem. Does anyone still make those geared correction units that you run inline on the speedo drive cable? Are you absolutely sure you don't have a Metric speedometer ? 100 KPH is 62.5 MPH. would also affect the odometer. "Occam's razor", the simplest solution is probably the correct one. 1 Quote Link to comment
Metzman510 Posted February 23, 2020 Author Report Share Posted February 23, 2020 Ok, first, that explanation of the speedometer function is over the top helpful! Thanks! Second, how would I know if I had a metric speedo? Would there be a KPH designation somewhere? Going for an odo run to check it shortly... Loving the help! Quote Link to comment
datzenmike Posted February 23, 2020 Report Share Posted February 23, 2020 This is a US speedo so no KPH markings, although maybe cars today might have both. In Canada there would be an outer and inner ring of numbers. The outer ring on after '74 speedometers would be in KPH and in smaller numbers inside this MPH. Quote Link to comment
Metzman510 Posted February 24, 2020 Author Report Share Posted February 24, 2020 Ok, so here's where I'm at... Speedo is marked MPH, clearly on the face. On a 10 mile loop as laid out in my bone stock Ram pickup, my odo reads 11.3 miles, off by 13%. So my 19 tooth speedo pinion needs to be a 20 tooth. 10% correction per tooth right? Maybe 21 would be better but sounds like it's very difficult to get... Once l get that new speedo pinion in the car I can start working on the speedo accuracy, which as Mike suggested is likely a magnetic adjustment issue. Any comments are appreciated. Quote Link to comment
datzenmike Posted February 24, 2020 Report Share Posted February 24, 2020 19/20 is 5.2% a 21 tooth would be 10.5% and as close as you will get. That's barely 1/2 MPH out at 50. 21 tooth is purple. The sleeve that holds the plastic gear is offset to allow 3 or maybe 4 different gear tooth counts. This is because the diameter increases as you add teeth. A 16 tooth would have less off set. You might be able to use a 21 in place of a 19 but if not it won't go in without crushing the plastic. I would take the speedometer pinion out and post a picture of it. The S12 200sx has a pinion that is 21 tooth but not much use if too short. Quote Link to comment
Metzman510 Posted February 24, 2020 Author Report Share Posted February 24, 2020 What year is an s12 200sx? Do you have the pn? I have access to a full machine shop and can modify as needed if possible. Quote Link to comment
datzenmike Posted February 24, 2020 Report Share Posted February 24, 2020 It was mentioned earlier that the shorty uses a different or longer pinion sleeve. This is why I mentioned removing it and taking a picture of it to see. Quote Link to comment
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